Sites and apps similar to BoxCoding include CodePen, which has a free version. Other options are jsFiddle, JSPad, JS Bin and vscode.dev. Code Editors like BoxCoding are a crowded field, with more than 50 alternatives for self-hosting, Mac, Windows, Linux and Android.
HtmlSave.com help you to save and host your HTML files online and give Rendered HTML link. This service is providing a simple playground for playing with HTML codes. This website is really helpful for testing how an HTML file will look in a browser.
Codeply is a editor that lets you run and preview your HTML, CSS and JavaScript code from any modern Web-browser. You've seen this capability in other tools like JSFiddle, Codepen and Bootply. But, Codeply is different because it's not just a code editor.
